1. Field of the Invention
This invention pertains to the arrangement for removal of captive fasteners.
2. Description of Prior Art
Captive fasteners currently are in wide use, offering obvious advantages in that the fastener element is retained to the part and always available for being secured after the part has been loosened. One of the more advantageous captive fasteners is disclosed in U.S. Pat. No. 3,765,465 pertaining to a captive nut which is adapted to made with a stud on an adjoining part. The nut has a flush head at one end, from which extends a cylindrical exterior surface that meets with a frustoconical surface, converging toward the opposite end of the nut and terminating at a radial shoulder. Beyond the shoulder is a short cylindrical section of the same exterior diameter as that of the first portion. The nut is received within a grommet which has a flush head at one end and a relatively thin wall at the opposite end. The grommet is extended through an opening in a workpiece and the thin-walled portion is flared outwardly to form a flange that cooperates with the head in holding the grommet to the workpiece. The grommet has an internal annular groove which receives a retainer ring which encircles the exterior of the nut, being slidable along its principal cylindrical surface and the frustoconical portion. When the retainer ring engages the shoulder of the nut, it prevents withdrawal of the nut from the grommet in one direction. Thus, the nut is held to the grommet and hence to the workpiece.
Fasteners of this type frequently are used with thin panels which may not have much strength. On advanced military aircraft, for example, the grommet may be attached to a thin graphite panel. This presents a difficulty in the event the nut becomes damaged and needs to be replaced. Because the retainer ring prevents the nut from being withdrawn from the grommet it has been necessary to remove the entire assembly, including the grommet, from the workpiece. This is difficult to do without damaging the workpiece, particularly where the workpiece is relatively thin. An axial force on the grommet sufficient to straighten out the flared portion so that the grommet can be taken from the opening in the panel often will damage the panel. fastener replacement, therefore, has been a relatively slow, expensive and unsatisfactory operation.